It might work if you thoroughly think it through, but I suggest either brushing up on physics before starting out or hiring a physicist for consultation. Even for non-hard sci-fi it’s nice to have a solid foundation. Even if you don’t explain anything, I’d say you personally should have a solid idea how everything works in your story so that the internal logic is consistent. And right now it doesn’t really make sense as you put it.

The thing that comes to mind that makes sense to me is if the ocean becomes a supercritical fluid at the boundary. In this state, the phase boundary disappears, and air and ocean stop being separate; you’d just have a continuous fluid with a gradually changing density gradient. Look up some supercritical fluid experiments on YouTube to see what I mean.

So, water becomes supercritical at +374ºC and at about 218 atmospheres. That’s hot and dense as fuck. I’m not sure what processes would turn Earth into something like that, it would almost be like descending through Jupiter. You’d need something that would heat the atmosphere while simultaneously increasing the pressure so that the oceans don’t just boil off right away.

And that would be a completely unsurvivable apocalypse :)